1. Field of the Invention
The present invention relates to a motor, a rotor, and a manufacturing process of the rotor.
2. Description of the Related Art
A so-called inner rotor type motor in which a rotor is disposed inside an armature is known. The types of rotors used in the inner rotor type motor are mainly classified into an SPM (Surface Permanent Magnet) type rotor in which a plurality of magnets are attached to the outer circumferential surface of a rotor core and an IPM (Interior Permanent Magnet) type rotor in which magnets are buried into a rotor core.
When the SPM type rotor is used, the armature and the magnets can be placed in proximity to each other. Therefore, the magnetic force of the magnets can be effectively used. However, in the SPM type rotor, measures to prevent the magnets from escaping outward due to a centrifugal force during high-speed rotation need to be prepared. On the other hand, when the IPM type rotor is used, there is no concern of the magnets escaping due to the centrifugal force. Therefore, recently, the IPM type rotor has been the mainstream.
However, in general, in any of the SPM type and IPM type rotors, each of the magnets is disposed so that a pair of magnetic pole surfaces are respectively directed radially outward and radially inward. Therefore, only the magnetic pole surface on the radially outside surface of the magnet contributes to motor driving. In order to effectively use the pair of magnetic pole surfaces of the magnet, a rotor structure in which magnets and cores of magnetic bodies are alternately arranged in the circumferential direction has been proposed.
A conventional rotor in which the magnets and the cores are alternately arranged in the circumferential direction is disclosed in, for example, Japanese Patent Application Publication no. 2010-063285. The rotor in Japanese Patent Application Publication no. 2010-063285 includes a rotor core, and substantially rectangular parallelepiped-shaped magnets accommodated in a plurality of slots formed in the rotator core, respectively (See, for example, paragraph [0059] of Japanese Patent Application Publication no. 2010-063285). In addition, in Japanese Patent Application Publication no. 2010-063285, the entirety of the magnets of the rotor are covered with a sealing resin (See, for example, paragraph 0063 of Japanese Patent Application Publication no. 2010-063285). Accordingly, the holding force of the magnets is increased (See, for example, paragraph [0064] of Japanese Patent Application Publication no. 2010-063285).
In FIG. 5 of Japanese Patent Application Publication no. 2010-063285, a gate through which the sealing resin is injected into a forming mold is provided at an upward position in the vicinity of the end portion on the radial outside of the magnets. According to the related art, it is thought that the gate is disposed in such a position because it is important to reliably cover the radially outside surface of the magnets with the sealing resin. However, when the position of the gate is eccentrically disposed radially outward, it is difficult for the resin to flow uniformly toward a through-hole positioned farther radially inward than the gate and toward the radial inner side of the magnets. In order to increase the rigidity of the sealing resin, molding the sealing resin with favorable accuracy even in the through-hole and on the radial inside of the magnets is required.